*Material downloaded from http:/brilliantcoaching.blogspot.com*

*BRILLIANT COACHING*

*Electricity Numericals*

*1. The current passing through a room heater has been halved. What will happen to the heat produced by it?*

*2. An electric iron of resistance 20 ohm draws a current of 5 amperes. Calculate the heat produced in 30 seconds.*

*3. An electric heater of resistance 8 ohm takes a current of 15 A from the mains supply line. Calculate the rate at which heat is developed in the heater.*

*4. A resistance of 40 ohms and one of 60 ohms are arranged in series across 220 volt supply. Find the heat in joules produced by this combination in half a minute*

*5. A resistance of 25 ohm is connected to a 12 V battery. Calculate the heat energy in joules generated per minute.*

*6. 100 joules of heat is produced per second in a 4 ohm resistor. What is the potential difference across the resistor?*

*7. An electric iron is connected to the mains power supply of 220 V. When the electric iron is adjusted at minimum heating’ it consumes a power of 360 W but at ‘maximum heating’ it takes a power of 840 W. Calculate the current and resistance in each case.*

*8. Ten bulbs are connected in a series circuit to a power supply line. Ten identical bulbs are connected in a parallel circuit to an identical power supply line.*

*A. Which circuit would have the highest voltage across each bulb*

*B. In which circuit would the bulbs be brighter?*

*C. In which circuit, if one bulb blows out, all others will stop glowing?*

*D. Which circuit would have less current in it?*

*9. Calculate the cost of operating a heater of 500 W for 20 hours at the rate of Rs. 3.90 per unit.*

*10. Which has a greater resistance, a 100 watt bulb or a 60 watt bulb?*

*11. How much energy is consumed when a current of 5 amperes flows through the filament (or element) of a heater having resistance of 100 ohms for two hours? Express it in joules.*

*12. An electric bulb is rated at 220 V, 100 W. What is its resistance?*

*13. An electric bulb is connected to a 220 V power supply line. If the bulb draws a current of 0.5 A, calculate the power of the bulb.*

*14. In which of the following cases more electrical energy is consumed per hour?*

*A. A current of 1 ampere passed through a resistance of 300 ohms*

*B. A current of 2 amperes passed through a resistance of 100 ohms.*

*15. Electric kettle rated at 220 V, 2.2 kW, works for 3 hours. Find he energy consumed and the current drawn.*

*16. In a house two 60 W electric bulbs are lighted for 4 hours, and three 100 W bulbs for 5 hours everyday. Calculate the electric energy consumed in 30 days.*

*17. If the potential difference between the ends of a wire of fixed resistance is doubled, by how much does the electric power increase?*

*18. A bulb is rated as 250 V; 0.4 A. Find its : (i) power, and (ii) resistance.*

*19. For a heater rated at 4 kW and 220 V, calculate (a) the current, b) the resistance of the heater, ) the energy consumed in 2 hours, and d) the cost if 1 kWh is priced at Rs. 4.60.*

*20. An electric motor takes 5 amperes current from a 220 volt supply line. Calculate the power of the motor arid electrical energy consumed by it in 2 hours.*

*21. Which uses more energy: a 250 W TV set in 1 hour or a 1200 W Toaster in 10 minutes?*

*22. An electric bulb is rated as 10 W, 220 V. How many of these bulbs can be connected in parallel across the two wires of 220 V supply line if the maximum current which can be drawn is 5 A.*

*23. How much work is done in moving a charge of 2 coulombs from a point at 118 volts to a point at 128 volts?*

*24. What possible values of resultant resistance one can get by combining two resistances, one of value 2 ohm and the other 6 ohm?*

*25. If 3 resistances of 3 ohm each are connected in parallel, what will be their total resistance?*

*26. If five resistances, each of value 0.2 ohm, are connected in series, what will be the resultant resistance?*

*27. Four resistances of 16 ohms each are connected in parallel. Four such combinations are connected in series. What is the total resistance?*

*28. An electric bulb of resistance 20 and a resistance wire of 4 are connected in series with a 6 V battery. Draw the circuit diagram and calculate (i)the total resistance of the circuit.(ii) Current through the circuit. (iii)Potential difference across the electric bulb.(iv)Potential difference across the resistance wire.*

*29. How will you connect three resistors of 2 ohm, 3 ohm and 5 ohm respectively so as to obtain a resultant resistance of 2.5 ohm? Draw the diagram to show the arrangement.*

*30. How will you connect three resistors of resistances 2ohm, 3 ohm and 6 ohm to obtain a total resistance of: (a) 4 ohm, and (b) 1 ohm?*

*31. A wire of resistance R is cut into five equal pieces. These five pieces of wire are then connected in parallel. If the resultant resistance of this combination be R then the ratio of resultant to the original will be?*

*32. A copper wire has a diameter of 0.5 mm and resistivity of 1.6 x 10 m.*

*A. What will be the length of this wire to make its resistance 10 2ohm?*

*B. How much does the resistance change if the diameter is doubled?*

*33. An electric heater which is connected to a 220 V supply line has two resistance coils A and B of 24 resistances each. These coils can be used separately (one at a time), in series or in parallel. Calculate the current drawn when*

*A. Only one coil A is used.*

*B. Coils A and B are used in series.*

*C. Coils A and B are used in parallel.*

*34. If the length of a wire is doubled by taking more of wire, what happens to its resistance?*

*35. How does the resistance of a wire change when*

*A. Its length is tripled?*

*B. Its diameter is tripled?*

*C. Its material is changed to one whose resistivity is three times?*

*36. How much energy is given to each coulomb of charge passing through a 6 V battery?*

*37. The potential difference between the terminals of an electric iron is 240 V and the current is 5.0 A. What is the resistance of the electric iron?*

*38. A potential difference of 20 volts is applied across the ends of a resistance of 5 ohms. What current will flow in the resistance?*

*39. A resistance of 20 ohms has a current of 2 amperes flowing in it. What potential difference is there between its ends?*

*40. A current of 5 amperes flows through a wire whose ends are at a potential difference of 3 volts. Calculate the resistance of the wire.*

*41. The resistance of an electric lamp filament is 230 ohms. The lamp is switched on when the line voltage is 115 volts. What is the current in the lamp circuit?*

*42. What is the potential difference between the ends of a conductor of 16 ohm resistance, when a current of 1.5 A flows through it?*

*43. Calculate the work done in moving a charge of 4 coulombs from a point at 220 volts to another point at 230 volts.*

*44. What is the potential difference between the terminals of a battery if 250 joules of work is required to transfer 20 coulombs of charge from one terminal of the battery to the other?*

*45. How much work is done in moving a charge of 2 C across two points having a potential difference of 12 V?*

*46. An electric bulb draws a current of 0.25 A for 20 minutes. Calculate the amount of electric charge that flows through the circuit.*

*47. A radio set draws a current of 0.36 A for 15 minutes. Calculate the amount of electric charge that flows through the circuit.*

*48. Potential difference between two points of a wire carrying 2 ampere current is 0.1 volt. Calculate the resistance between these points.*

*49. A simple electric circuit has a 24 V battery and a resistor of 60 ohms. What will be the current in the circuit? The resistance of the connecting wires is negligible.*

*50. A wire of resistance R is cut into five equal pieces. These five pieces of wire are then connected in parallel. If the resultant resistance of this combination be R then the ratio of resultant to the original will be?*

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*http:/brilliantcoaching.blogspot.com*